Data Validation (List) too long

I hate to drag this thread out of the grave but I'd love some help. I've read all the post above and downloaded all the examples but I really don't understand how they work.

I am trying to put a huge formula into the Data Validation "Source:" field but it is too long. I need to fit this into a 255 character space...

=IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Airport Plow",Airport_Plow_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Industrial Combo",Industrial_Combo_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Industrial Lift Group",Industrial_Lift_Group_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Industrial Loader Adaptor",Industrial_Loader_Adapter_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Industrial Plow",Industrial_Plow_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Industrial Wing",Industrial_Wing_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Multiple Uses See Tags",Multiple_Uses_See_Tags_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Truck Hitch (Truck Portion)",Truck_Hitch_Truck_Portion_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Truck Plow",Truck_Plow_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Truck Spreader",Truck_Spreader_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Truck UBS",Truck_UBS_Series,IF(CONCATENATE(Sheet1!A3," ",Sheet1!B3)="Truck Wing",Truck_Wing_Series,Sheet1!C1))))))))))))

I'll include my file in case anyone is interested in looking at it with me.

Essentially my issue is the same as the original poster's but I don't not understand how he solved his issue.